The present invention relates to respirators and more particularly to powered air respirators for use in dusty or debris laden atmospheres or, in atmospheres contaminated with toxic dusts, mists or fumes provided that suitable filter media are utilized.
Much effort has been expended in efforts to provide respiratory, eye and face protection to workers exposed to dust and debris in the atmosphere. Examples of such devices are disclosed in Depping U.S. Pat. No. 3,413,972, Guy U.S. Pat. No. 3,822,698, Bancroft U.S. Pat. No. 3,963,021, Lowe and Odell U.S. Pat. No. 4,133,308, and Gorman U.S. Pat. No. 4,136,688. However, each of these devices proved to be disadvantageous in one or more respects. Perhaps the major disadvantage of these prior art devices has been the gap between the user's chin and the lower edge of the visor found in Guy U.S. Pat. No. 3,822,698, Bancroft U.S. Pat. No. 3,963,021, Lowe et al. U.S. Pat. No. 4,133,308 and Gorman U.S. Pat. No. 4,136,688. While it has been suggested that the gap could be minimized or even eliminated if an exhaust valve were incorporated into the lower edge of the visor, it has been reported that even a small opening at the chin has permitted the intrusion of particles from grinding operations. It is expected that the exhaust valve, which would always be open under the operating pressures encountered, would itself be an opening through which particles from grinding operations could enter the visor. Devices which fully enclose the head and shoulders of a user are quite cumbersome to wear and restrict freedom of movement.